JPS59218261A - Washing method of printed board and automatic soldering device provided with washing device - Google Patents

Abstract

PURPOSE:To improve reliability of a soldered part by washing a printed board soldered by a soldering device, in a state that it is kept at >=60 deg.C to wash completely a flux residue. CONSTITUTION:A printed board is soldered by an automatic soldering device provided with a fluxer, a pre-heater, a solder tank, a cooling device, etc. The printed board soldered by this automatic soldering device is washed by a washing device in a state that it is kept at a temperature of >=60 deg.C by a heater. According to said method, a flux residue is washed completely, and reliability of a soldered part is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a method for cleaning flux residue attached to a printed circuit board soldering surface after soldering with an automatic soldering device, and an automatic soldering device equipped with a cleaning device. Regarding equipment.

Soldering of printed circuit boards is carried out by applying flux to the surface of the printed circuit board, preheating it, immersing it in molten solder, and cooling it. When soldering printed circuit boards used in conventional electronic devices with a flux containing pine resin as a main component, pine resin has some degree of insulating properties, so there is no problem even if the flux residue is not removed after soldering. However, in electronic equipment that requires high precision, there is a growing demand for thorough cleaning even from substances such as pine tar.

In addition, when soldering materials that do not have good soldering properties using automatic soldering equipment, ZnO62 or NH,01
A water-soluble flux containing highly active chlorides is sometimes used, but since the flux residue is corrosive, it must be cleaned after soldering.

Conventionally, in automatic soldering, printed circuit boards that were soldered using a device that needed to be cleaned of flux residue were appropriately cleaned using a cleaning device, but complete cleaning was not possible. The inventor of the present invention investigated the cause of this problem and found that the printed circuit board was sufficiently cooled after soldering, making it impossible to completely clean the board. In other words, if the temperature of the printed circuit board after soldering drops too much, the flux residue will solidify, making it difficult to clean. For this reason, it may be possible to reheat a printed circuit board whose temperature has dropped too much to raise the temperature before cleaning it, but the flux residue could not be completely removed even if the reheated circuit board was cleaned. This is because the flux residue, once solidified by cooling, does not soften easily even when reheated, making it difficult to remove with a cleaning solution.

The present invention has been made by focusing on the above-mentioned characteristics of flux residue, and it is an object of the present invention to provide a cleaning method and an automatic soldering device equipped with a cleaning device that facilitate the removal of flux residue after soldering. .

The present invention will be explained below with reference to the drawings. Figure 1 is a schematic diagram of an automatic soldering device according to the present invention.
1) is a fluxer, (2) is a preheater, (3) is a solder bath, (4) is a cooler, (5) is a heater, and (6) is a cleaning device. In the automatic soldering described above, the soldering and cleaning of the printed circuit board by the apparatus is performed in the following steps.

■ When soldering the printed circuit board (P), slack is applied to the surface using fluxer (1).

Flux application is essential for soldering work, and when soldering printed circuit boards, it must be applied evenly to the surface.

■ Place the flux-coated printed circuit board in a preheater (2
) Preheat.

Preheating the flux-applied surface activates the flux and at the same time raises the temperature of the soldering part, resulting in better soldering properties.

Furthermore, preheating softens the heat effect when immersing in high-temperature molten solder.

■ Soldering of a printed circuit board is performed by dipping the surface into a solder bath (3) containing molten solder.

At this time, the slack is replaced by molten solder on the soldered parts to which flux has been applied, but the flux is again deposited on top of the solder. Most of the parts that are not soldered still have flux attached to them.

■ Cool the printed circuit board after soldering using a cooler (4).

After soldering, if the solder remains molten on the soldering part for a long time, the soldering part may move due to vibration, which may cause cracks in the solder or separation of the lead and the soldering part. .

Therefore, after soldering, the parts to be soldered must be immediately cooled to below the melting temperature of the solder using a cooler. However, in the present invention, the temperature of the printed circuit board during cooling is 60°C.
It must be ensured that the temperature does not drop below ℃.

■ After passing through the cooler, the printed circuit board is heated to a temperature suitable for the cleaning process that follows.
) to perform heating. The temperature of the printed circuit board at this time must be maintained at at least 60° C., but the heating temperature will be slightly higher if pine resin flux and water-soluble flux are used. That is, a temperature of 80 to 100°C is appropriate for a printed circuit board soldered with a pine resin flux, and a temperature of 60 to 80°C is appropriate for a water-soluble slack. This is because pine resin flux residue is easily soluble in organic solvents such as triclene and perchloroethylene at 80 to 100°C, and water-soluble flux residue is less soluble in hot water at 60 to 80°C.

■ The printed circuit board maintained at a predetermined temperature is cleaned using an appropriate cleaning device.

The cleaning effect will be best if the solvent used in the cleaning device (6) is kept at a temperature close to that of the printed circuit board, but if the printed circuit board is at an appropriate temperature, the temperature of the solvent will be close to the temperature of the printed circuit board. Even at low levels, the cleaning effect is sufficient. Note that any type of cleaning device that uses a solvent can be used.

Examples of the present invention will now be described.

Pine tar 70% by weight, jetanolamine HBr 1% by weight
A pine resin-based flux printed circuit board made of PA is foam-coated with a fluxer, heated in a preheater for 48 seconds to raise the temperature to 90°C, and 27 seconds later, a eutectic composition molten solder (280°C) is applied. ℃) for 7 seconds in a static solder bath. Then, 18 seconds after leaving the solder bath, the blower's cooler is used to cool the solder.
After 0 seconds, the printed circuit board, which had dropped to 100°C, was heated with a heater and, while being maintained at 90°C, was transferred to the next cleaning step, and the flux residue was cleaned with a cleaning device using trichlene. The temperature change of the printed circuit board at this time becomes a graph as shown in FIG. As is clear from this graph, the printed circuit board that has been cooled by the cooler is heated by the heater before it has completely cooled down, so it is possible to proceed to the next cleaning process while being maintained at a predetermined temperature. In other words, since the flux residue is washed in a state where it is easily soluble in the solvent, complete cleaning can be performed.

For comparison with the present invention, the graph of the temperature change of the printed circuit board after soldering is performed using the same automatic soldering device as shown in FIG. 1 except for the heater (5) until cleaning is shown. Shown in Figure 2. For this soldering, we soldered the printed circuit board &! The temperature after cooling with the cooler is 5
Because the temperature had dropped to 0°C, the cleaning equipment was not sufficient to clean it, and it was observed that flux residue remained in the grooves attached to the printed circuit board.

As described above, the present invention can provide a reliable soldering section for high-precision electronic equipment because flux residue can be completely cleaned.

[Brief explanation of the drawing]

Figure 1 is a schematic diagram of the automatic soldering device of the present invention and a graph showing the temperature change of the printed circuit board. Figure 2 is a schematic diagram of the conventional automatic soldering device and a graph showing the temperature change of the printed circuit board when soldering is performed using the device. This is a graph showing. ■...Fluxer 2...Preheater 3...Solder bath 4...Cooler 5...Heater 6...Cleaning device patent applicant Senju Metal Industry Co., Ltd. Procedural amendment (method) Kazuo Wakasugi, Commissioner of the Japan Patent Office, dated September 7, 1982, Incident Description, Patent Application No. 91512, filed in 1982, Title of Invention: Automatic soldering device equipped with printed circuit board cleaning method and cleaning device 3. Relationship with the case of the person making the amendment Patent applicant 4. Date of amendment order August 10, 1980 (Shipping date: August 30, 1988) 5. Application and specification to be amended 6. Contents (1) Amend the attached application form and specification. (2) The text "Fig. 3" on page 8, line 11 of the specification should be corrected to "Fig. 2."that's all

Claims (1)

[Claims] (11 Automatic soldering of printed circuit boards involves soldering using a fluxer, preheater, soldering bath, cooling device, etc. installed in the device, and then maintaining the printed circuit board at a temperature of 60°C or higher using a heater. A method for cleaning printed circuit boards characterized by cleaning with a cleaning device. (2) For automatic soldering equipped with a fluxer, a preheater, a soldering bath, a cooler, etc., the device uses a heating device and a cleaning device after the cooling device. Automatic soldering equipment characterized by sequential installation of equipment.